SuzukiSavage.com - Pilot jets with holes in the sides vs no holes

DavidOfMA

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Pilot jets with holes in the sides vs no holes
12/03/12 at 09:33:30

I'm trying to find the best balance between preventing backfiring and not stalling when choked. Going to a 55 pilot jet helped with backfiring but the bike won't idle when choked even with the idle mix screw turned almost all the way in.

I have two 52.5 pilot jets, one with holes in the side and the other with no holes. Which is the richer jet? I am hoping if I put in the richer "standard" pilot jet, I will be able to find a better idle mix screw setting rich enough to reduce backfiring but not so rich the bike won't run when choked.

Thanks!

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- David

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Serowbot

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Re: Pilot jets with holes in the sides vs no holes
Reply #1 - 12/03/12 at 10:02:27

If there's a difference (and I don't think there is),.. I'd go with the extra holes...

... but,.. keep in mind... a 20% change in humidity will make more than one jet size difference anyway... 2k of elevation,... 20f temp...

Jetting, is not that precise... it's just finding a good average...
#55 sounds like it's too much... when in doubt go for the smaller pilot... (it'll help mpg's)...

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Dave

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Re: Pilot jets with holes in the sides vs no holes
Reply #2 - 12/03/12 at 15:50:50

I did a little research on it, and I believe the holes in the sides of the Pilot Jets are used in carbs that use and "air" screw for adjusting the idle mixture. Our bikes adjust the flow of gasoline - while some adjust the flow rate of air. In those carbs that use air it is bled into the side of the Pilot Jet through those side holes.

So......using a Pilot Jet with or without holes doesn't make any difference in our bikes.

I agree that you need to use the smallest Pilot Jet that allows you to adjust your idle fuel mixture properly. If you have to open the idle mixture screw 3 turns or more to get the engine to run smoothly - then it is too lean. I believe a 52.5 is the biggest you might need, but mine runs best with a 50.0......and a 150 main.....and I have adjusted the slide needle until it runs best. (Someday I need to measure the thickness of the washers).

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DavidOfMA

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Re: Pilot jets with holes in the sides vs no holes
Reply #3 - 12/03/12 at 15:53:30

I was hoping there was some kind of intermediate jet between 52.5 and 55. At least in my area, with current weather, the bike seems too lean with a 52.5 and the idle mix screw turned out 3 turns. It backfires. With the 55 jet and the idle mix screw turned out 1/2 turn, it doesn't backfire much but stalls out at idle when cold. Something like a 53.75 jet seems like it would be the best compromise. I'd hoped the ones with air holes on the side were a little richer. What else would have the same effect?

Thanks.

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- David

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Serowbot YaBB Moderator ModSquad Offline OK.... so what's the speed of dark? Posts: 28678 Tucson Az Gender:	Re: Pilot jets with holes in the sides vs no holes Reply #4 - 12/03/12 at 16:09:03 How's your idle speed?... It's not real lopey slow, is it?... You'll cook yer' cam with a slow idle speed...
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ralfyguy

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Re: Pilot jets with holes in the sides vs no holes
Reply #5 - 12/03/12 at 16:19:30

DavidOfMA wrote on 12/03/12 at 15:53:30:

I was hoping there was some kind of intermediate jet between 52.5 and 55. At least in my area, with current weather, the bike seems too lean with a 52.5 and the idle mix screw turned out 3 turns. It backfires. With the 55 jet and the idle mix screw turned out 1/2 turn, it doesn't backfire much but stalls out at idle when cold. Something like a 53.75 jet seems like it would be the best compromise. I'd hoped the ones with air holes on the side were a little richer. What else would have the same effect?

Thanks.

I was in the same boat. 52.5 too lean, 55 too rich. What I did was make my own in between. Since I didn't have any small enough drill bits, I found me a safety pin that was too big to fit the 52.5, and would fall loosely into the 55. Then I took a grinder to the tip of the needle and shaped it like a screwdriver tip. Then I put the needle in the vise and force twisted the 52.5 all the way through. If you keep twisting and backing out frequently, the needle will go through eventually. There is only about a 1/4" of brass to go through.
Now I have a jet that is in between the two and it runs just great.
Although i wish it would've been a tad smaller as the the mixture screw is only about a 1/4 turn out versus 2 1/2 turns before. I wish it would have been around 1 turn out to have a little more adjustment if necessary.
But it's fine the way it is now.

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Cavi Mike

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Re: Pilot jets with holes in the sides vs no holes
Reply #6 - 12/03/12 at 16:20:40

I'm not sure I understand the question. What does your choke have to do with this? Have you been needing to ride around with your choke on just to keep the bike running or are you talking about when you first start it cold? Either way - you don't tune the carb to how the bike runs with the choke pulled. How the choke makes the bike run has to do with the choke, not the jets.

Another thing - there are 2 or 3 notches in the choke, not one. You may just not be putting the choke where it needs to be to keep the bike running.

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LANCER Serious Thumper Alliance Member Offline Savage Beast Performance Parts Posts: 10668 Oklahoma Gender:	Re: Pilot jets with holes in the sides vs no holes Reply #7 - 12/03/12 at 16:49:33 There is no difference between the 2types of jets for the AMOUNT of fuel they will flow. The theoretical difference between them is that the one with holes will transition between throttle settings more smoothly.
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DavidOfMA

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Re: Pilot jets with holes in the sides vs no holes
Reply #8 - 12/03/12 at 17:13:56

Cavi Mike wrote on 12/03/12 at 16:20:40:

I'm not sure I understand the question. What does your choke have to do with this? Have you been needing to ride around with your choke on just to keep the bike running or are you talking about when you first start it cold? Either way - you don't tune the carb to how the bike runs with the choke pulled. How the choke makes the bike run has to do with the choke, not the jets.

Another thing - there are 2 or 3 notches in the choke, not one. You may just not be putting the choke where it needs to be to keep the bike running.

Since I went to the 55 pilot jet, the bike stalls when cold when I give it any amount of choke (but won't idle with no choke, either). It didn't do that with the 52.5 jet, but with the 52.5 jet it backfired. Going to the 55 jet mostly fixed the backfiring but seems to have caused the cold idle stalling problem. I have to palm the throttle to keep it from stalling at stop signs until it's warmed up.

Once it's warm enough to run with no choke, it runs pretty well with the 55 pilot jet. Finding a jetting balance between not backfiring and not stalling at cold idle is what I'm looking for.

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« Last Edit: 12/03/12 at 18:50:30 by DavidOfMA »

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DavidOfMA

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Re: Pilot jets with holes in the sides vs no holes
Reply #9 - 12/03/12 at 18:52:19

Quote:

I was in the same boat. 52.5 too lean, 55 too rich. What I did was make my own in between. Since I didn't have any small enough drill bits, I found me a safety pin that was too big to fit the 52.5, and would fall loosely into the 55. Then I took a grinder to the tip of the needle and shaped it like a screwdriver tip. Then I put the needle in the vise and force twisted the 52.5 all the way through. If you keep twisting and backing out frequently, the needle will go through eventually. There is only about a 1/4" of brass to go through.
Now I have a jet that is in between the two and it runs just great.
Although i wish it would've been a tad smaller as the the mixture screw is only about a 1/4 turn out versus 2 1/2 turns before. I wish it would have been around 1 turn out to have a little more adjustment if necessary.
But it's fine the way it is now.

Thanks, that's an interesting idea! I had considered the possibility but didn't really know how to proceed.

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SinglesGoinSteady Full Member Offline SuzukiSavage.com Rocks like Bon Scott! Posts: 130 From Seattle, now in Savannah. Gender:	Re: Pilot jets with holes in the sides vs no holes Reply #10 - 12/03/12 at 20:07:54 You can always drill it out bigger, solder it, then drill it out to the exact diameter you want it if you have the bits.
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LANCER Serious Thumper Alliance Member Offline Savage Beast Performance Parts Posts: 10668 Oklahoma Gender:	Re: Pilot jets with holes in the sides vs no holes Reply #11 - 12/04/12 at 03:55:36 If the stock carb is functioning as designed, the pilot jets should have about a 1/3 overlap from one size to the next size. Ex: say you have. 52.5 @ 2.5 turns out, replace it with a 55, then you should find the same state of tune at about 1 turn out. +/- a little.
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strang Senior Member Offline Posts: 387 london Gender:	Re: Pilot jets with holes in the sides vs no holes Reply #12 - 12/04/12 at 04:50:09 A couple of weeks ago I did a back and forth with the stock jet (no holes) and aftermarket (with holes) of same sizes - didn't notice one bit of difference. oh and that troll thread disappearing has just made me more paranoid
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DavidOfMA

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Re: Pilot jets with holes in the sides vs no holes
Reply #13 - 12/04/12 at 05:11:30

LANCER wrote on 12/04/12 at 03:55:36:

If the stock carb is functioning as designed, the pilot jets should have about a 1/3 overlap from one size to the next size. Ex: say you have. 52.5 @ 2.5 turns out, replace it with a 55, then you should find the same state of tune at about 1 turn out. +/- a little.

Thanks. This is really helpful info for troubleshooting, as that's not what I'm experiencing.

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DavidOfMA

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Re: Pilot jets with holes in the sides vs no holes
Reply #14 - 12/04/12 at 05:13:14

strang wrote on 12/04/12 at 04:50:09:

A couple of weeks ago I did a back and forth with the stock jet (no holes) and aftermarket (with holes) of same sizes - didn't notice one bit of difference.
oh and that troll thread disappearing has just made me more paranoid Shocked

Thanks. Then that eliminates trying the jet with holes.

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